Weather balloons are used to release radiosondes into the atmosphere. The sondes house a collection of measuring devices. This instrument box measures temperature and air humidity. In addition, the weather balloons are equipped with GPS to enable them to determine altitude, flight path, wind speed and wind direction. A radio transmitter allows the measurement data to be transmitted in real time.
MeteoSwiss releases a weather balloon twice a day: From Monday to Friday, the balloons are launched manually at 11 AM UTC, and automatically at the same time at weekends; the second launch at 11 PM UTC is always automatic. The sounding station is located in Payerne, where data from the atmosphere has been collected since the 1940s.
The hydrogen-filled weather balloons ascend at a speed of around five metres per second, taking approximately two hours to reach an altitude of 30-35 km.